1. Field of the Invention
The present invention relates to a sheet supply apparatus and an image forming apparatus that pick up one sheet at a time from a stack of sheets by using air pressure and feed the sheet to a conveying path.
2. Description of Related Art
As an invention related to a conventional sheet supply apparatus, a sheet supply apparatus described in Japanese Patent Laid-Open Publication No. 2010-254462, for example, is known. FIG. 35 illustrates the structure of a sheet supply apparatus 100 described in Japanese Patent Laid-Open Publication No. 2010-254462.
In the sheet supply apparatus 100, an air blowing section 102 blows air toward the upper end (the end of the z axis in the positive direction) of a stack S of sheets to float a sheet S1, which is the topmost sheet. An endless suction belt 104 with many through-holes is placed above the stack S of sheets. A chamber (not illustrated), which is placed inside the suction belt 104, uses its built-in fan to withdraw air from between the stack S of sheets and the suction belt 104 through these through-holes, and then attaches the topmost sheet S1 to the suction belt 104. The suction belt 104 is rotated by the driving force of a motor (not illustrated). Thus, the attached sheet is conveyed in the x direction to an acceptance port 108 of a conveying path 106. Then, the topmost sheet S1 passes through the conveying path 106 and is conveyed to an imaging unit (not illustrated).
The sheet supply apparatus 100 further has an image capture section 110 and a control circuit 112. The image capture section 110 captures an image of the floated sheet S1 and a sheet immediately below the sheet S1 at a position away from a side surface P1 of the stack S of sheets by a prescribed distance in the y direction. The control circuit 112 calculates a clearance between these sheets from an image captured by the image capture section 110. The control circuit 112 also adjusts the amount of air to be blown by the air blowing section 102, according to the calculated clearance between the sheets.
In the sheet supply apparatus 100, the stack S of sheets is accommodated in a case 114 of the sheet supply apparatus 100, so the interior of the sheet supply apparatus 100 is dark, making it difficult for the image capture section 110 to capture an image of sheets. Therefore, it is also difficult for the control circuit 112 to calculate a clearance between sheets according to the image captured by the image capture section 110.